1. Field of the Invention
The present invention relates to the technique of processing data recorded in the form of an arrangement of atoms or molecules, by using an atomic probe incorporated in a system, such as a scanning tunneling microscope (STM), which is designed to form a three-dimensional image showing atomic structure. In the case of an STM, a tunnel-current probe is used as the atomic probe. In the case of an atomic force microscope (AFM), an atomic force probe is used as the atomic probe. In magnetic domains, a magnetic force probe is used as the atomic probe. The STM, which can read data in the form of an arrangement of atoms, comprises a very small piezoelectric-element driven cantilever made by an integrated circuit ("IC") process and measuring 1 mm.times.200 .mu.m.times.5 .mu.m, and a sharp probe also made by an IC process and attached to free end of the cantilever. This STM, generally known as cantilever-type STM or micro STM, is used along with a specific data-recording medium, thus constituting a so-called microelectronic device. More specifically, the present invention relates to, for example, a circuit having a temporary storage area using a micro STM and, more particularly, to a micro STM arithmetic circuit device constituting circuits such as a sampling circuit, a delay circuit, a shift register, and a bit inversion circuit. The present invention also relates to a micro STM recording apparatus which enables reading or writing of information using a micro STM and to a micro STM recording medium for us with the micro STM recording apparatus.
2. Description of the Related Art
Heretofore, various constituent elements for electronic circuits have been proposed as is well known. These elements have been improved in performance, size, cost, and stabilization.
In recent years, on the other hand, applications of the scanning tunneling microscope (STM) invented by Binning, Rohrer, et al. to various fields have been studied. The STM is disclosed in an article entitled "Surface Studies by Scanning Tunneling Microscope" by G. Binning, H. Rohrer, Ch. Gerber, and E. Weibel, Physical Review Letters, Vol. 49, No. 1, pp 57-61 (Jul. 5, 1982). That is, when a direct-current voltage is applied between a sample and a tunnel current probe with the tip of the probe placed at a distance of several nanometers from the sample surface, electrons travel between the sample surface and the probe because of the tunnel effect. The STM utilizes the phenomenon.
More specifically, the STM is processed such that the tip of the tunnel current probe is sharpened to be less than 1 .mu.m and one atom of atoms constituting the probe protrudes from its portion approaching the atomic structure of the sample. A servo circuit is added to a detector for detecting a tunnel current flowing between the probe and the sample so as to drive a piezoelectric actuator for controlling the probe-to-sample distance. The probe is scanned two-dimensionally along the surface of the sample. Thereby, the STM can output variations in the tunnel current and the atomic structure as a three-dimensional space. In this type of STM, the up-and-down motion of the probe corresponds to the atomic structure profile of the sample.
It has also been found that the tunnel current flowing between the probe and the sample depends upon the probe-to-sample distance and the work functions of substances constituting the probe and the sample. Thus, the current obtained from the probe scanning the sample varies in response to irregularities formed on the sample, the kind of atoms constituting the substance of the sample, or electric charges trapped in the vicinity of the sample surface.
On the other hand, an attempt has been made to directly draw a pattern on a silicon substrate by means of the STM. For example, in an article entitled "Lithography with the Scanning Tunneling Microscope"by M. A. McCord and R. F. W. Pease, J. Vac. Sci. Technol. B. Vol. 4, No. 1 Jan/Feb 1986, pp. 86-88, it is reported that tracks were engraved on a thin film of gold deposited on a silicon substrate by scanning an STM at an applied energy of 10 eV. In the same journal, a report is made on a write line formed on a 10-nm thick Langmiur Blodgett (LB) film of decosenoic acid by means of a beam of 25 V and 12 nA.
Furthermore, such a micro STM as announced under the title of "A Planar Process for Microfabrication of STM" by C. F. Quate, M. J. Zdeblick, T. R. Albrecht, and S. Akamine at the University of Stanford in the Third International Conference on Scanning Tunneling Microscope (Oxford 4-8 July, 1988) includes an extremely small piezoelectric-element driven cantilever which measures 1 mm.times.200 .mu.m.times.5 .mu.m and uses ZnO made by an IC process as a piezoelectric element and a sharp probe evaporated onto the tip of the cantilever using a small hole as a mask by an IC process.
C. F. Quate invented an STM memory using the micro STM in which the displacement (representing the presence or absence of recorded information) on the scanning surface of a sample (recording medium) or in the neighborhood of the surface of the sample is read as a variation in tunnel current by scanning the probe, the STM memory being now patented under U.S. Pat. No. 4,575,822, entitled "METHOD AND MEANS FOR DATA STORAGE USING TUNNEL CURRENT DATA READOUT". The STM can attain an incomparable recording density. Thus it is possible to make a sample (recording medium) on which information is recorded very small as compared with recording mediums used in conventional information recording apparatuses.
However, though having described the formation of a micro STM memory using a cantilever type of micro STM as described above, C. F. Quate has disclosed none of formats for recording information.
In addition, no attempt has been made to apply such a micro STM as described above to various types of arithmetic circuit devices constituting electronic circuits.
The probe used in the AFM has one atom on its tip, like the probe incorporated in the STM. This atom interacts with the atoms placed on the recording medium and recognized as protrusions representing data, thus generating Coulomb force or Van der Waals force, thereby reading the data. Like the STM probe, the AFM probe is servo-controlled by means of a piezoelectric element, whereby the gap between the tip of the probe and the surface of the recording medium is maintained. The AFM probe can be incorporated into the micro STM cantilever described above. It can be used in place of the magnetic force probe which is applied to read data from magnetic domains. The tip of the AFT probe can be made of artificial diamond vapor-deposited on the free end of a cantilever. If this is the case, the AFT probe can accurately read data from the atoms placed on the surface of the recording medium, while being driven by drive pulses.